"I cannot express my anger enough that those close to me have unfairly been dragged into this," she added at the time.

"As the details of the case emerge people will see today as an expensive sideshow, and a waste of public money as a result of this weak and unjust decision."

Charlie Brooks, a writer and racehorse trainer, said that he and the four others were being used as "scapegoats" in an attempt by police to "ratchet up the pressure on my wife, who I believe is the subject of a witch hunt".

He added: "There are 172 police officers, about the equivalent of eight murder squads, working on this; so it doesn't surprise me that the pressure is on to prosecute, no matter how weak the cases will be."

Their day in court comes ahead of the appearance tomorrow by David Cameron at the Leveson Inquiry, which was set up by the prime minister to investigate media ethics and standards in the wake of the hacking scandal.

Cameron is expected to be quizzed on his relationship with media figures, including Brooks and her former boss, the billionaire News Corporation boss Rupert Murdoch.